If you really want an app to do that Doubletwist is a pretty good one. They also have a wireless solution, Airsync. But you could just pop out your SD card, connect it to your PC and drag and drop your files directly to it. Just create a folder on the SD card named "music" and put your files in the folder. The music apps on the phone will find the files. You could also connect your phone to your PC and do the same thing without taking the SD card out. You just need to go to Samsung's website, go to support, look up your phone and download the USB drivers and install them on your PC. If you have downloaded Samsung Kies you already have the drivers installed. Just connect your phone, open Windows Explorer and browse down to your phone and the SD card. Putting the files directly onto your SD card will not carry over any playlists though, you'll have to recreate them on the phone. Another solution is to use Google Music. You download Google Music Manager to your PC, it will find all your music and import it - to include playlists. Then just open The Play Music app on your phone and your music is there for you. This is a streaming service but you can "pin" your music to your phone. By doing that (pin) it caches your music to your phone for offline listening.

^^^ beat me to it well that's assuming he has a micro SD card reader or a usb reader if you don't here's the alternitive just plug in your phone go to your start bar look to the rite you will see computer open it and you should see the gs4 listed as a device double click find the SD card double click open it rite click new file title it music open the new file keep this window open go back to your start bar if you dont see a music file on the left go back to computer look on the left you should see your user folders or music folder open it drag and drop you do know if you use Google Music you can download the music manager and upload all of your music from your computer and even download tracks you purchased rite??

Do you have an SD card installed? Does your computer have a card reader. Again if so, remove the memory card from the phone and install it in the computers card reader. Create a music folder on your memory card and copy your music to it. Remove the card from your computer and put it back in your phone. I put 15gb of music on my phone this way and to works without a hitch. I find it easier to transfer music from computer to Android Galaxy this way. Especially if you have a lot of files to move.

If you use Google Music you can make it download directly to your sd and it will read music off of your sd card I don't even bother with Kies if your on a windows machine simply hook your phone to the USB port press the start bar go to computer and look for your phone double click on it it should pop up two storage options one will be your sd card and the other will be your internal open your sd card find your music folder then go to start bar find music open up your computer's music folder and you can drag and drop or you can even use windows media player